ferret



UNITED STATES ATENT MICHEL FERRET, OF'LYONS, FRANCE.

FlRE-GRATE.

SPECIFICATION formingpart of Letters Patent No. 236,252, dated January4, 1881.

Application filed August 13, 1880. (N0 model.) PatentedinFrauce July 28,1877.

To all whom it may concern:

Be it known that I, MICHEL PERRET, manufacturer, a citizen of theRepublic of France, andresiding in Lyons, France, have inventedImprovements in Fire-Grates, (for which I have obtained a French patent,July 28,1877, No. 119,651,) of which the following is a specification.

This invention relates to a particular disposition of fire-grates whichpermits the realization of certain conditions very important withrespect to a good combustion-conditions which have not heretofore beenobtained.

In all industrial furnaces the bars of the tiregrates are separated adistance calculated according to the fuel employed, the volume of air tobe admitted in a given time, and, in general, according to the multipleconditions imposed by the particular result which it is desiredtoobtain; but, however exact the rela-' ti've proportions may be at thebeginning, the normal supply ofair intended lasts but a little while, onaccount of the expansion and clogging of the bars, which change thesections of the air-passages, and also on account ofcthe rapiddestruction of the grate. The last objection is specially noticeable infires provided with forced blasts, and it is perhaps to be attributed tothis that this class of fires is received with so small favor,notwithstanding the advantages they afford in many cases. Thedisposition which I employ has the effect of preventing all warping, ofmaintaining the metal at a constant temperature, which assuresuniformity in the conditions whereon the passage of the air through thelimited orifices or air-spaces depends, of facilitating the clearingofthe grate, and of assuring its preservation.

The grate that is adopted is composed of a series of bars of sufficientdepth to dip into water in such manner as to be constantly kept cool,and consequently protected from rapid destruction. To this end theentire grate is placed in abox, which may be of strong sheet-' of theblast, which passes between the water and the grate andfthen through theopenings in the latter. Another orifice serves for feeding the water, soas to maintain it at the proper level.

A suitable opening also permits the ashes which fall into the water insmall quantities to be withdrawn. The difference of expansion betweenthe part of the bars which is in immediate contact with the fire andthat which is cooled by immersion would naturally produce tensionstending to break the metal. This difficulty is avoided by the shape ofthe cooling-plates. These are comparatively thin and deep, and decreasein length toward the bottom, where the length is approximately equal toor less than the depth. As a further security, in some casesperpendicular openings or slots are formed in the plates, and then thedepth should be equal to or exceed the length between the ends of theplates and the slots, or between the slots where there are two or more.Equal expansion of all the parts is thus secured.

Heretofore a grate has been devised in which the bars are provided onthe bottom with webs that dip in the water-trough below. These webs are,however, comparatively long, thick, shallow, and are continuous, andeach is provided with an independent trough, the draft or air blastpassing between the troughs. This part of the present'inventiondifferstherefrom in the shape of cooling-plates, in the use ofperpendicular openings or slots in such plates, and in the commonwater-vessel which forms the bath in which a series of cooling-platesdip, so that the blast or draft passes over the surface of said waterand between the said plates. The cooling of the grate lowers thetemperature of the ashes on its surface, prelower surface of sufficientdepth to plunge into the sheet of water placed-beneath, andto preservealways the space necessary for the introduction of air between the levelof the water and the surface upon which the fuel burns. The cooling dueto the partial immer-i sion of the grate, by assuring the permanence oftheir forms, permits the sections of the airholes to be exactlydetermined.

It is possible to reduce the sections as much as may be necessary forthe employment of dry and pulverulentfuel; but with openings ofsubstantially uniform section at a certain reducti0ntwo millimeters, forexample-the air passes with difficulty, an excess of pressure becomesnecessary, and gives rise to pai tial lifts of the fuel, and consequentinequalities in the passage of the air, and an irregular burning of thefire.

I have devised a simple means whereby the passage of air throughopenings the most reduced in horizontal section, and of any suitableform, is facilitated. This means consists in the widening or beveling ofthe upper part of the openings near the fuel, so as to give to the air amore extended surface, and at the same time an oblique direction, whichpermits all parts of the fuel to be properly reached. The regularpassage of the air through thin layers of fuel, with a pressure of onlyafew centimeters of water, is thus secured. This disposition can beadapted to furnaces which are not provided with a blast, and permits thereduction in cross-section of the air-passages by facilitating thepenetration of the airin the layers of the fuel.

Experience has shown that the quantity of water evaporated by thecontact of the gratebars is not important, even in case hot air is used.The water-vapor produced has, in fact, a real utility. By itsdecomposition it tends to lower the temperature of the fire-bed,whichwould have a bad efi'ect upon the exposed parts of the heater, and thecombustion of the hydrogen restores, at a distance from the fire, theabsorbed heat, producing flames even in case of fuels which ordinarilyburn without flame, such as pure anthracite.

The immersion of the bars, of which the particular object is to coolthem, can be dispensed with by giving them a sufficient depth andthickness. This feature has a special importance for application tolocomotive-furnaces. Under these conditions the refrigerating agentwould be air. In other cases steam taken from the boiler could beemployed, it being blown between or under the bars in such manner as tocool the plates, which are then surrounded by steam, instead of beingplunged into water, as above indicated.

The possibility of employing hot air without alteration in the grate isvery advantageous in furnaces supplied with a blast, since it permitsthe recovery of heat from the gases of combustion, this heat not beingnecessary for creating a draft. The recovery of part of the heat can beaccomplished by divers means. I have employed metallic tubes presentinga large surface.

In the accompanying drawings, which form a part of this specification, Ihave represented some of the forms which can be adopted for realizingthe principles of my invention, without, however, intending to confinemyself to these forms, which are eminently variable, according to theobject and principal purpose of the grate.

On all the figures, A represents the gratebars, which are, as shown, ofconsiderable depth, so as to form cooling-plates a, and which dip intothe water-bath B.

Figure 1 illustrates, by views in side elevation, plan, and section, theconstruction of one type of grate-bar. It is provided with a verticalopening or slot, a, in the plate a, to enable it to withstand the actionof cooling.

In Fig. 2 is represented a style of bar with only a small portion of itscooling-plate immersed.

By examining the views in elevation and section on dotted lines in viewin elevation, it will be seen that the thickness and depth of the bar orplate will vary with the distance from the cooling-liquid in such manneras to carry off the heat, and thus prevent the excessive heating andrapid destruction of the grate.

In Fig.3, which consists of views in side elevation and central verticalsection, the cooling-plate is trapezoidal in form. It can also be madetriangular, as shown in dotted lines.

Fig. 4 is a plan, and Fig. 5 a section, of a partially-immersed grateformed of bars notched or cut away at the sides, so that when placedtogether a series of cross or star shaped holes are formed, very smallat the bottom, but inclined or flaring at the top, as indicated at a. Anoblique direction is thus given to the air, which permits it to reachall parts of the fuel.

In Fig. 6, which consists of views in side elevation and section on thedotted line, the cooling-plate is provided with two openings or slots,and is somewhat moditied in form from that shown in Fig. 1.

My system of grates presents special advantages in connection with firesor furnaces having a forward blast; but the principles enunciated areapplicable as well to fires burning by an internal draft.

Having thus explained the said invention and the manner of carrying thesame into effect, what I claim, and desire to secure by Letters Patent,is

1. A fire-grate provided with cooling-plates of the form shown, the samebeing comparatively thin and decreasing in length toward the bottom, andhaving a depth approximately equal to or greater than the length at thelower part of the plates between the ends, or between the ends and oneor more vertical slots in the plates, substantially as described.

2. A grate-bar having a comparatively thin depending cooling-plateextending longitudinally of said bar, and being of a depth approximatelyequal to or greater than the length of the plate at the bottom, betweenits ends, or between the ends and one or more vertical over the surfaceof the water-bath in the vessel and between the plates, substantially asdescribed.

6. A fire-grate provided with cooling-plates and having contractedair-openings inclined or flaring on the top, substantiallyas described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

MICHEL FERRET.

Witnesses:

H. FESOHOTTE, GEORGE PEIXOTTO.

